制冷机组突然停电时应先关闭（）。
A.吸气阀
B.排气阀
C.节流阀
D.供液阀
参考答案：A
Don't _____ me now. I must go. I am late. [ ]
A. speak
B. say
C. talk
D. speak to
客人对账单收费怀疑不愿付款时怎么办？
